ARCHIVED REPORTS_XR0009848 - Laserfiche WebLink

Home Browse Search

that Benzene, Toluene, Xylene, & TPH-G were measured in all four wells, at various depths ranging from 11 ' to bottom. The amounts of contamination increased with depth, and were highest gust above or within the water table, wh3_ch was measured at approx- imately 68' bgl. Copies of the laboratory reports and chain of custody sheets for the soil samples are included as APPENDIX K TABLE VII summarizes the results of the laboratory analyzes of the water samples collected on June 3 by Del Tech Significant levels of BTEX & TPH--G were detected 3_n all four wells, which supports the data from the bottom soil samples, (which were within the water table. ) Copies of the .Laboratory reports and chain of custody are included as APPENDIX L. The highest level, of Benzene were measured in MW--1 , (11 ,000 ug/L, ) followed by MW--3, (8, 600 ug/L, ) and lower amounts in wells #2 & 09 The same pattern was measured for TPH--G, (#1 highest, #4 lowest. ) The levels of Toluene, Ethylbenzene & Xylene found did not conform exactly to the same pattern, but were detected in all wells. The levels measured indicate that the hydraulic gradient is towards the northeast; however, as shown on PLATE X, the gradient as measured on June 3 was towards the south, in the direction of . MW-3 . The regional gradient as measured by County Flood Control District maps is almost due west; the gradient measured in the monitoring wells on the U. S. Chemical property to the southeast was also in westerly direction, quite different from that measured on the Canteen property. If the hydraulic gradient on this site was primarily westerly, MW-4 should have measured the highest levels of contamination. In fact, that well had the lowest Benzene & TPH-G levels of the four, and was second lowest in Ethylbenzene and third lowest in Xylene MW-1 , which is located upgrad3_ent based on regional and U S Chemical data, and only slightly downgradient based on the data 3_n this report, had the highest measured amounts of all compounds except Ethylbenzene, which was found in relatively small amounts in all 4 wells. This suggests that either. ( 1 ) the groundwater gradient is subject to frequent changes 3_n direction, or (2) , an off-site source of contamination exists to the east and/or north- east of the property. At this time, there 3_s insufficient data to determine whether or not the removed UST was the only source of the contamination. CONCLUSIONS Based on the results of the work done on the property as described in this report, the following conclusions can be made- 1) Laboratory analysis of soil samples taken during soil boring & 15